Debugging C++ classes using library String class

I’m trying to debug classes which use the Watcom String-class. When not
using the String class i can debug my own classes and browse to the class
members by clicking on this in the debugger. When using the String class,
i’m not able to debug the members anymore. Does somebody know what is wrong?
I’m using Watcom C++ 10.6 on QNX 4.23, and compile using cc whet -g option
turned on.

Regards Gustaaf